1. Field of the Invention
The invention relates generally to conductors and electrical cables, and more particularly to an electrical composite conductor and an electrical cable using carbon nanotubes to enhance electrical conductivity.
2. Description of Related Art
Electrical cables are used as a carrier to transfer electrical power and data signals. An electrical cable includes at least one conductor core and an insulating jacket surrounding the conductor. The conductor core requires good electrical conductivity. The insulating jacket is needed to fulfill certain mechanical and electrical properties, such as fire prevention and protection of the conductor core. Further, the electrical cables can include EMI (electromagnetic interference) shielding layers.
Copper or copper alloys are usually selected as conductor materials in electrical cables. Copper has good electrical conductivity, but suffers from problems like eddy current loss and RF (radio frequency) signal decay due to EMI. Eddy current loss is power loss (usually in the form of heat) in an electrical cable. In addition, heat is generated when current flows through the conductor of the electrical cable. The amount of heat generated is proportional to the resistance of the conductor. The resistance of the conductor is directly proportional to its length and inversely proportional to its cross-sectional area. EMI can be emitted by electrical circuits carrying rapidly changing signals as a by-product of their normal operation and can cause unwanted signals (interference or noise) to be induced in other circuits.
Many electrical cables, such as seismic, oceanographic, and telephone cables are used in corrosive environments at pressures that may range from atmospheric to very high and at temperatures that may range from arctic to very high. Accordingly, the insulating materials used in such cables must be able to withstand these harsh environments, as well as have the insulating and capacitive properties desirable for cables. Polymers, such as PVC, are selected as materials of the electrical cable exterior insulator. However, it is difficult for devices using polymers to meet the European Union's new RoHS (restriction of hazardous substances) standards as polymers may are often highly inflammable and toxic.
What is needed, therefore, is a conductor having better electrical conductivity than copper and an electrical cable using the same that can satisfy RoHS.